Hydrodynamic Analysis of Ducted Marine Turbine: Study on the Duct and Turbine Efficiency

This paper presents a boundary element method applied to the numerical prediction of ducted turbine performance. The model turbine is a horizontal axis marine current turbine subject to the uniform inflow. For this type of steady problem, BEM runs much faster than a finite-volume-method-based viscous simulation, thus facilitating the analysis of different turbine configurations. The primary purpose of this study is to investigate how different duct shapes and loading conditions affect ducted turbine performance compared to those from open turbines. Unlike a lifting line model, a commonly used technique for turbine research, the present method does not require simplifying the turbine geometry and trailing wake. Instead, the blade and duct trailing wakes are fully aligned based on the local stream representing the expansion/contraction of the trailing wakes and their mutual interactions. Predicted force and power coefficients are compared with open turbine performance to see how the presence of the duct influences the overall turbine efficiency. The predicted results show that the ducted turbine performance is significantly affected by the flow induced by the duct and its vertical elevation from the blade tip.